How good might the Boston Celtics be with Kemba Walker?
The Celtics will reportedly strike early in free agency Sunday, when they are expected to formalize an agreement with the former Charlotte Hornets point guard on a four-year max deal worth a reported $140-plus million.
In Walker, Boston would get another All-Star point guard to replace Kyrie Irving. But the Celtics still must figure out how to fill Al Horford's role at center on the cheap, as he, like Irving, is expected to leave.
So what can we expect from Boston this season and beyond?
Walker's production similar to Irving's
By signing Walker, the Celtics would come about as close to possible as replicating Irving's skill set. The two point guards were All-NBA picks last season (Irving on the second team, Walker the third team) and a version of my SCHOENE similarity scores using strictly 2018-19 performance shows only Damian Lillard of the Portland Trail Blazers as more similar to both players than they were to each other.
There are some differences between the two players. Walker is a bit more pick-and-roll dominant. He averaged 55.8 ball screens per 100 possessions last season according to Second Spectrum tracking data, more than Irving (36.2), and in fact had the league's sixth-highest rate among players who ran at least 500 of them. Remarkably, that rate was actually down from the previous two seasons, when Walker ran at least 60 pick-and-rolls per 100 possessions.
In that regard, and in terms of his size (a listed 6-foot-1), Walker is in some ways a better match for Irving's Boston predecessor at point guard, Isaiah Thomas. Thomas averaged as many as 47.2 pick-and-rolls per 100 possessions in 2015-16, more similar to Walker's rate in Charlotte.
All three point guards share strong shooting ability that makes them 3-point threats off the dribble and forces defenders to chase them over screens. Only MVP runner-up James Harden made more pull-up 3-pointers per game last season (4.4) than Walker (2.1), according to Second Spectrum tracking on NBA Advanced Stats. Irving averaged 1.1 pull-up 3s last year but shot them at nearly an identical percentage (35.5%) to Walker (35.6%). Thomas, meanwhile, averaged 1.6 pull-up 3s per game at a 35.7% clip in 2016-17, his last season with the Celtics.
One possible adjustment for Walker in Boston would be spending more time playing without the ball. His 7.5 minutes average time of possession last season were fifth-most in the league according to NBA Advanced Stats and meant Walker had the ball in his hands more than 40% of the time the Hornets were on offense. Irving, by contrast, had just 5.5 minutes average time of possession, about a third of the time the Celtics had the ball with him in the game.
As with Irving, Walker's spot-up shooting ability should make him a threat when other Boston players are handling the ball. While he shot a subpar 34.8% on catch-and-shoot 3-point attempts in 2018-19, Walker made better than 40% in each of the previous four seasons.
From a pure talent perspective, Irving is clearly preferable to Walker. He's bigger and younger by almost two years, and he has been slightly more valuable. But with Irving's departure looking certain, Walker becomes an excellent save.
Unfortunately for Boston, it apparently will come at the same time as Boston loses the team's best frontcourt player as well as several other contributors. Now the Celtics have to replace them.
Boston thin up front
In order to create the cap space necessary to make Walker a max offer, Boston had to trade veteran center Aron Baynes and will presumably renounce the rights to free agents Horford, Irving, Marcus Morris and Terry Rozier.
(Hypothetically, the Celtics could acquire Walker in a multi-team double sign-and-trade involving either Horford or Irving while staying over the cap, but that scenario quickly becomes complicated and would subject both Boston and the team receiving Horford or Irving to a hard cap of $6.6 million more than the luxury-tax line.)
That set of moves will leave the Celtics' roster much thinner, particularly up front. Boston's center rotation now consists of 2018 first-round pick Robert Williams (who played 283 minutes as a rookie) and perhaps 2019 first-rounder Grant Williams (who measured shorter than 6-foot-6 without shoes at the NBA draft combine). The Celtics will likely be able to retain early Bird rights to Daniel Theis, a restricted free agent who can play either frontcourt spot. But their starter will almost certainly be signed later in free agency, most likely with the $4.8 million room midlevel exception.
More than almost any other team in recent memory, Boston appears poised to take advantage of the ease of finding contributors at center. Robert Williams was quite effective in his limited appearances last year, after all, putting up preposterous numbers. (He shot 70% from the field and blocked 12.5% of opponent 2-point attempts while committing 5.1 fouls per 36 minutes.) And the room midlevel could yield a productive player like Brooklyn Nets free agent backup Ed Davis or Richaun Holmes of the Phoenix Suns. The Celtics could cobble together a decent center rotation while spending less than $10 million on the position.
Elsewhere, Boston shedding depth would have pros and cons. It would assure larger, more regular roles for the team's wings who battled for playing time last year. Smart would likely play regularly at point guard while Jayson Tatum would be the probable starter at power forward, clearing wing minutes for Jaylen Brown and Gordon Hayward. At the same time, an injury or two on the wing could leave the Celtics short on rotation-caliber players.
Let's take a look at how my projections based on the multiyear, predictive version of ESPN's real plus-minus would forecast Boston, assuming Theis returns as a restricted free agent, as does Brad Wanamaker (unrestricted) and the room midlevel is used on a starting center.
Somewhat surprisingly, RPM projects the Celtics far stronger defensively than offensively even with the loss of Horford. Although he wasn't recognized with All-Defensive honors until last season, Smart has long been a standout defensively in RPM, while Tatum also rates well and Boston would have few defensive liabilities in the rotation.
Meanwhile, the Celtics' average offensive projection is partially the result of an adjustment that regresses players who change teams (like Walker) to the mean. Without that adjustment, Walker's offensive RPM would be plus-3.3 and Boston would improve a full point per 100 possessions as a team. But the Celtics would still decline due to the loss of Horford, whose replacement is unlikely to provide the same kind of floor spacing from the center spot.
Overall, the preliminary RPM projection for Boston would come in around 47-48 wins, depending on who the Celtics are able to add at center. That would be similar to last year's 49-win finish, although not as impressive as Boston's plus-4.4 point differential, which would typically translate to approximately 52 wins.
If you think Walker's fit with the Celtics will allow him to beat the RPM adjustment, taking it away would bump Boston up to around 50 wins. As compared to last year, when 49 wins were a huge disappointment because of sky-high expectations, getting to 50 wins this season would feel like a huge accomplishment for a team forced to regroup in free agency.